JP3083117B2 - Vehicle suspension system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling a damping coefficient of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device for controlling a damping coefficient of a shock absorber, for example, Japanese Unexamined Patent Publication No.
What is described in 163011 is known.

In this conventional vehicle suspension system, when the direction code of a sprung vertical speed signal obtained by processing a signal of a sprung vertical acceleration sensor and a relative speed signal between a sprung and unsprung speed are the same, a damping coefficient is obtained. Is hardened, and the damping coefficient is softened when the sign is different, and the damping coefficient is controlled independently for the four wheels.

[0004]

However, in the conventional apparatus described above, when a high frequency is input from under the spring, the control means switches between hardware and software in response to the high frequency. , The rise delay of the damping force, the switching time of the actuator, etc.
Although the control response is delayed, the vibration damping property against low-frequency input is improved, but there is a problem that the riding comfort cannot be improved when traveling on a rough road having many high-frequency components.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a vehicle suspension system capable of improving the riding comfort of a vehicle when traveling on a rough road. is there.

[0006]

[Means for Solving the Problems]

Therefore, in the present invention, at least the unsprung
Sprung cut-off low-frequency components below the vibration frequency range
The damping coefficient is controlled based on the vertical acceleration processing signal.
I tried to achieve my purpose.

The vehicle suspension system according to the first aspect is provided with a shock absorber b interposed between the vehicle body side and each wheel side and capable of changing a damping coefficient by damping coefficient changing means a, and each shock absorber b. A sprung vertical acceleration detecting means c for detecting a sprung vertical acceleration near a position where the shock absorber b is provided; a sprung vertical speed detecting means f for detecting a sprung vertical speed near a position where each shock absorber b is provided; From a sprung vertical acceleration signal obtained by the vertical acceleration detecting means c, a filter circuit d that cuts off at least a low frequency component less than the unsprung resonance frequency region, and a filter circuit d near a position where each shock absorber b is provided. Relative speed detecting means g for detecting a relative speed between sprung and unsprung;
The damping coefficient of each shock absorber b is increased by increasing the damping coefficient when the sprung vertical acceleration and the relative speed between the sprung and unsprung are the same sign, while controlling the damping coefficient to a minimum when the sprung vertical acceleration and the unsprung sign are different signs, When the processing signal of the vertical acceleration exceeds a predetermined threshold value, a damping coefficient control means e is provided for reducing the damping coefficient until a predetermined time elapses after the signal decreases below the threshold value. .

The filter circuit includes a high-pass filter that cuts off a low-frequency component below the unsprung resonance frequency region from a sprung vertical acceleration signal obtained by the sprung vertical acceleration detecting means, A low-pass filter that cuts off high-frequency components in the frequency region or higher may be configured.

[0010]

According to the sprung vertical acceleration signal obtained by each sprung vertical acceleration detecting means, a low frequency component below the unsprung resonance frequency region is cut off by passing through a filter circuit. High-frequency components above the region are obtained as processed value signals.

Since the frequency component in the unsprung resonance frequency region increases when traveling on a rough road compared to when traveling on a good road, the damping coefficient control means responds to the processed signal of the sprung vertical acceleration by the shock absorber. By performing the damping coefficient control, the riding comfort of the vehicle when traveling on a rough road can be improved.

[0012] Also, damping factor control means, and the relative speed between the vertical acceleration and the sprung-unsprung spring increases the damping coefficient when the same sign, when different signs to control the damping coefficient to a minimum Therefore, the damping property on the spring can be ensured.

On the other hand, even when the sprung vertical acceleration and the relative speed between the sprung and unsprung are to be controlled to have the same sign and a high damping coefficient, the processed signal of the sprung vertical acceleration processed by the filter circuit is generated. When a predetermined threshold value is exceeded, the damping coefficient is reduced until the predetermined time elapses after the pressure value falls below the threshold value, and thereby, the riding comfort of the vehicle when traveling on a rough road is reduced. Can be improved.

[0014]

An embodiment of the present invention will be described with reference to the drawings. (First Embodiment) First, the configuration will be described. FIG.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a configuration of a vehicle suspension system according to a first embodiment, in which four shock absorbers SA ₁ , SA ₂ , SA ₃ , and SA ₄ are provided between a vehicle body and four wheels. In the description, when these four are collectively referred to, and when the common configuration is described, they are simply indicated as SA.).
A vertical acceleration sensor (hereinafter, referred to as a vertical G sensor) 1 for detecting a sprung vertical acceleration is provided on the vehicle body near each shock absorber SA. Also,
At a position near the driver's seat, there is provided a control unit 4 that receives a signal from each sensor 1 and outputs a drive control signal to the pulse motor 3 of each shock absorber SA.

FIG. 3 is a system block diagram showing the above configuration. The control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a includes the above-mentioned sprung G sensor 1
And a signal from each load sensor (a relative speed detecting means between sprung and unsprung) 6 is input. The load sensor 6 is provided at a portion where the shock absorber SA is attached to the vehicle body, and detects a damping force F generated by the shock absorber SA as a load. Also,
In the interface circuit 4a, a set of two filter circuits 4d shown in FIG. That is, the HPF is a high-pass filter circuit that cuts off half the unsprung resonance frequency from the sprung acceleration signal sent from the upper and lower G sensors 1, and the LPF is sent from the upper and lower G sensors 1. A low-pass filter circuit that cuts off a frequency twice as high as the unsprung resonance frequency from among the sprung acceleration signals obtained. Can be extracted.

FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A is a cylinder 30, a piston 31 that defines the cylinder 30 in an upper chamber A and a lower chamber B, an outer cylinder 33 in which a reservoir chamber 32 is formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber 32. And a piston 32
A guide member 35 for guiding the sliding of the piston rod 7 connected to the outer cylinder 33, a suspension spring 36 interposed between the outer cylinder 33 and the vehicle body, and a bump rubber 37.

FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein, and An expansion damping valve 12 and a compression damping valve 20 for opening and closing 31a and 31b, respectively, are provided. A stud 38 fixed to the tip of the piston rod 7 and penetrating the piston 31 has an upper chamber A
A communication hole 39 that communicates with the lower chamber B is formed. Further, an adjuster 40 for changing the flow path cross-sectional area of the communication hole 39 and a communication hole 39 for the fluid in accordance with the direction of fluid flow.
An expansion-side check valve 17 and a compression-side check valve 22 that allow and shut off the flow of air are provided. The adjuster 40 is rotated by the pulse motor 3 (see FIG. 4). The stud 38 has a first port 21, a second port 13, a third port
A port 18, a fourth port 14, and a fifth port 16 are formed.

On the other hand, the adjuster 40 has a hollow portion 19, a first horizontal hole 24 and a second horizontal hole 25 communicating between the inside and outside, and a vertical groove 23 formed in the outer peripheral portion. I have.

Therefore, between the upper chamber A and the lower chamber B, as a flow path through which fluid can flow during the extension stroke, the inside of the extension side damping valve 12 passing through the through hole 31b is opened to open the lower chamber. B, the first port D on the extension side, the second port 13 and the flute 2
(3) a second expansion passage (E) that opens the outer peripheral side of the expansion damping valve (12) through the fourth port (14) to reach the lower chamber (B);
The extension side check valve 17 is opened via the port 13, the vertical groove 23, and the fifth port 16, and the extension side third valve reaching the lower chamber B is opened.
The flow path F, the third port 18, the second lateral hole 25, and the hollow portion 19
There are four flow paths of a bypass flow path G which leads to the lower chamber B via. Also, as a flow path through which fluid can flow in the pressure stroke,
The upper side chamber A is opened by opening the pressure side first flow path H passing through the through hole 31a and opening the pressure side damping valve 20, and opening the pressure side check valve 22 via the hollow portion 19, the first horizontal hole 24, and the first port 21. Pressure side second flow path J leading to the hollow portion 19, the second lateral hole 2
5, there are three flow paths: a bypass flow path G which reaches the upper chamber A via the third port 18.

That is, the shock absorber SA is configured such that the damping coefficient can be changed in multiple stages with characteristics as shown in FIG. 6 on both the extension side and the compression side by rotating the adjuster 40. That is, as shown in FIG. 7, a state where both the extension side and the compression side are soft (hereinafter, the soft area S
When the adjuster 40 is rotated counterclockwise from S), the damping coefficient can be changed in multiple stages only on the extension side, and the compression side becomes an area fixed to a low attenuation coefficient (hereinafter referred to as an extension side hard area HS). Conversely, when the adjuster 40 is rotated clockwise, the damping coefficient can be changed in multiple stages only on the compression side, and the expansion side becomes a region fixed to a low attenuation coefficient (hereinafter referred to as a compression side hard region SH). I have.

In FIG. 7, the KK section, the MM section, and the NN section in FIG. 5 when the adjuster 40 is arranged at the position of, are respectively shown in FIGS. FIG. 10 shows the damping force characteristics of each position in FIGS.

Next, the operation of the control unit 4 for controlling the driving of the pulse motor 3 will be described. In addition,
This control is performed separately for each shock absorber SA.

First, the rough road determination flow will be described with reference to the flowchart of FIG. 17 and the time chart of FIG.

In step 201, the sprung vertical acceleration obtained from each of the vertical G sensors 1 is calculated by using each of the filter circuits HPF,
This is a step of performing processing for obtaining a processing signal V ₀ of the sprung vertical acceleration in which the signal is passed through the LPF and cut off outside the unsprung resonance frequency region.

Step 202 is a step of judging whether or not the processing signal V ₀ of the sprung vertical acceleration has exceeded a predetermined threshold value V _S.
If NO (less than threshold value V _S ), the routine proceeds to step 204.

In step 203, the threshold value exceeding flag F is set.
This is a step of turning on flag 1, and thereafter, the routine proceeds to step 205, where the rough road flag is turned on.

Step 204 is a step F.
This is a step of turning off the flag 1, and then the process proceeds to step 206.

Step 206 is a step for judging whether or not the previous processing signal V ₀ of the sprung vertical acceleration has exceeded a predetermined threshold value V _S.
Proceed to 7, and if NO (less than previous threshold value V _S ), step 2
Proceed to 08.

Step 207 is a step for clearing the timer count.

Step 208 is a step for judging whether or not the timer count has exceeded the control delay time T _S , and proceeds to Step 211 with YES, and proceeds to Step 209 with NO (less than the control delay time T _S ).

Step 209 is a step of adding 1 to the timer count, and then proceeds to step 210.

In step 210, the delay flag Fla
g2 is turned on, and then step 20
Go to 5.

In step 211, the delay flag Fla
g2 is turned off, and then step 2
Proceed to 12 to turn off the rough road flag.

That is, in the rough road determination flow, the threshold crossing flag Flag1 or the delay flag Fla
When at least one of g2 is ON, it is determined that the road is bad, and the bad road flag is turned ON. In other cases, the bad road flag is turned OFF.

Next, the damping coefficient control operation of the control unit 4 will be described with reference to the flowchart of FIG. 15 and the time chart of FIG.

Step 101 is a sprung vertical speed signal V
This is a step for determining whether or not the relative speed F between the sprung and unsprung portions has the same sign. The process proceeds to step 103 with YES, and proceeds to step 102 with NO (symbol).

Step 102 comprises a shock absorber S
The damping coefficient of A is controlled so that both the extension and the pressure become the lowest damping coefficients. That is, the shock absorber SA is controlled to the soft area SS (the area in FIG. 7).

Step 103 is a step for determining whether or not the rough road flag is ON.
The process proceeds to step 105 if NO (bad road flag is OFF).

In step 104, a predetermined medium attenuation coefficient is controlled. That is, the shock absorber SA is controlled to the extension-side hard area HS or the compression-side hard area SH such that the same stroke side as the direction of the sprung speed at that time is the predetermined medium damping coefficient and the reverse stroke is the lowest damping coefficient. .

In step 105, when the damping force is F = kV
(Note that k is a proportionality constant.) The attenuation coefficient is proportionally controlled. That is, the shock absorber SA is connected to the extension-side hard region HS (see FIG. 3) such that the same stroke side as the direction of the sprung speed at that time has a high damping coefficient proportional to the sprung vertical speed V and the reverse stroke has the lowest damping coefficient. 7) or the compression side hard area SH (FIG. 7 side).

Next, the operation of the embodiment will be described with reference to the time chart of FIG.

(A) Running on a normal road When the vehicle runs on a normal road, the value of the sprung vertical acceleration near the unsprung resonance frequency is small, and the sprung vertical acceleration signal value V ₀ becomes a predetermined threshold V _Since it is less than _S , when the sprung vertical speed V and the relative speed F have the same sign, that is, when the damping force is acting in the damping direction, the shock in the same direction as the sprung vertical speed V at that time is applied. Control the stroke side of the absorber SA to a high damping coefficient proportional to the sprung vertical velocity V, and to the minimum damping coefficient when the sign is different, that is, when the damping force is acting in the vibration direction. Accordingly, vibration of the vehicle body at the time of low-frequency input can be suppressed, and steering stability of the vehicle can be ensured.

(B) Running on a Bad Road When the vehicle is running on a bad road, the value of the sprung vertical acceleration near the unsprung resonance frequency increases, and the sprung vertical acceleration signal value V ₀ becomes a predetermined threshold V for more than _S, at this time,
After that, the control delay time T falls below the threshold value.
Until _S elapses, the sprung vertical velocity V and the relative velocity F
Even if the same sign is used, by controlling the stroke side of the shock absorber SA in the same direction as the direction of the sprung vertical speed V at that time to the medium damping coefficient M, the ride comfort of the vehicle at the time of high frequency input is improved. Can be.

As described above, in the vehicle suspension system of the first embodiment, the driving comfort of the vehicle when traveling on a rough road is improved while ensuring the steering stability of the vehicle when traveling on a normal road. The feature is that it can be.

Next, the second embodiment will be described. In describing the second embodiment, only the differences from the first embodiment will be described. Further, the same reference numerals in the description as those in the first embodiment indicate the same objects.

In the second embodiment, the shock absorber S
As A, as a variable damping coefficient type, when the pulse motor 3 is driven, as shown in FIG. 19, a known structure in which both the expansion side and the compression side change from high attenuation to low attenuation (for example, (Refer to the public relations of Japanese Utility Model Publication No. 63-112914)
This is an example using.

In the second embodiment, as shown in the time chart of FIG. 20, the expansion and compression strokes of the shock absorber SA are determined by the high damping coefficient H, the medium damping coefficient M, and the minimum damping coefficient S. In three stages.

Although the embodiment has been described above, the specific configuration is not limited to this embodiment, and any change in the design without departing from the gist of the present invention is included in the present invention.

For example, in the embodiment, as an example of the reduction of the damping coefficient when traveling on a rough road, the case where the middle damping coefficient is controlled between high and low is shown. It may be.

Further, in the embodiment, one set of the filter circuit is used for the HPF and the LPF, but the LPF may be omitted.

[0051]

As described above, in the vehicle suspension system of the present invention, the sprung vertical acceleration signal obtained by the sprung vertical acceleration detecting means is obtained by using a high-pass filter.
By controlling the damping coefficient of each shock absorber based on the processed signal value of the sprung vertical acceleration in which low-frequency components below the unsprung resonance frequency region have been cut off, the ride comfort of the vehicle when traveling on rough roads Can be improved.

[0052] Also, the damping coefficient of the shock absorbers, and the relative speed between the vertical acceleration and the sprung-unsprung spring increases the damping coefficient when the same sign, the minimum to control the damping coefficient when different signs On the other hand, when the processing signal of the sprung vertical acceleration processed by the filter circuit exceeds a predetermined threshold value, the damping coefficient is reduced until the predetermined time elapses after the processing signal falls below the threshold value after the predetermined time elapses. With the provision of the damping coefficient control means, it is possible to obtain an effect that it is possible to improve the riding comfort of the vehicle when traveling on a rough road while securing the steering stability of the vehicle when traveling on a normal road.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a claim showing a vehicle suspension system of the present invention.

FIG. 2 is a configuration explanatory view showing a vehicle suspension system according to a first embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system according to a first embodiment.

FIG. 4 is a sectional view showing a shock absorber applied to the first embodiment device.

FIG. 5 is an enlarged sectional view showing a main part of the shock absorber.

FIG. 6 is a damping force characteristic diagram corresponding to a piston speed of the shock absorber.

FIG. 7 is a damping coefficient characteristic diagram corresponding to a step position of a pulse motor of the shock absorber.

FIG. 8 is a perspective view of the shock absorber shown in FIG.
It is -K sectional drawing.

FIG. 9 is a perspective view of the shock absorber shown in FIG.
It is a -M sectional view.

FIG. 10 is a sectional view taken along line NN of FIG. 5 showing a main part of the shock absorber.

FIG. 11 is a damping force characteristic diagram when the shock absorber is on the extension side hard.

FIG. 12 is a damping force characteristic diagram of the shock absorber in a soft state on an extension side and a compression side.

FIG. 13 is a damping force characteristic diagram of the shock absorber in a pressure-side hard state.

FIG. 14 is a block diagram showing a main part of the control unit of the first embodiment.

FIG. 15 is a flowchart showing a control operation of the control unit of the first embodiment.

FIG. 16 is a time chart showing the operation of the first embodiment.

FIG. 17 shows the control operation of the control unit;
It is a flowchart which shows operation | movement of a rough road determination flow part.

FIG. 18 is a time chart showing a control operation of the rough road determination flow portion.

FIG. 19 is a characteristic diagram of a damping coefficient of a shock absorber of the device of the second embodiment.

FIG. 20 is a time chart showing the control operation of the control unit of the second embodiment.

[Explanation of symbols]

 a damping coefficient changing means b shock absorber c sprung vertical acceleration detecting means d filter circuit e damping coefficient controlling means f sprung vertical speed detecting means g sprung and unsprung relative speed detecting means

Claims (2)

(57) [Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping coefficient by damping coefficient changing means, and detecting a sprung vertical acceleration near a position where each shock absorber is provided. A sprung vertical acceleration detecting means, a sprung vertical speed detecting means for detecting a sprung vertical velocity near a position where each shock absorber is provided, and a sprung vertical acceleration signal obtained by the sprung vertical acceleration detecting means. A filter circuit that cuts off at least low-frequency components below the unsprung resonance frequency region, and a spring near the position where each shock absorber is provided.
Relative speed detection means for detecting the relative speed between the upper and lower springs, and the damping coefficient of each shock absorber
When the relative speed between sprung and unsprung has the same sign, the damping
Increase the number and control the attenuation coefficient to the minimum when the sign is different
On the other hand, the sprung vertical acceleration processed by the filter circuit
When the processed signal exceeds a predetermined threshold,
Between the time the value falls below the maximum value and the time specified
A vehicle suspension system comprising: damping coefficient control means for reducing a damping coefficient. 2. The method according to claim 1, wherein the filter circuit includes
In the sprung vertical acceleration signal obtained by the speed detection means
Low-frequency components below the unsprung resonance frequency range
High-pass filter and unsprung resonance frequency range
Low-pass fill that cuts off the above high-frequency components
Data and that is constituted by a vehicle suspension system according to claim 1, wherein.